The overall objective of this research is to determine if integrins participate in the process of egg activation at fertilization. This will be investigated in a number of ways. First, the presence and localization of the alpha integrin subunit, an integrin subunit likely to participate in amphibian fertilization, will be determined using immunoblotting and immunofluorescence techniques. A specific Beta subunit will be looked for using immunoprecipitation and immunoblotting. Second, a functional role for integrins at fertilization will be examined using function-blocking antibodies against integrin subunits to interfere with sperm-egg fusion and/or egg activation. The third objective is to determine whether activating integrins on the egg surface stimulates events of egg activation, including production of phosphatidylinositol 4,5- bisphosphate, changes in membrane potential, an increase in intracellular Ca2+, elevation of the fertilization envelope, cortical contraction, second polar body formation, and actin accumulation in the region of sperm entry. The final objective is to introduce the subunits for the putative mammalian integrin sperm receptor into Xenopus eggs and to examine whether their expression allows mouse sperm to fuse with frog eggs and initiate egg activation. These studies will contribute to our understanding of the basic biology of fertilization. This background may ultimately find applications to practical problems such as contraception and infertility.